In the dental and orthodontic field it is often necessary to break an adhesive bond that has been formed between two dental structures. For example, the removing of orthodontic bands or brackets from teeth at the completion of treatment. Typically, orthodontic brackets are removed by mechanical devices with the application of a force. These devices generally comprise various types of orthodontic pliers or mechanical arms that can be used as levers. Orthodontic bracket removing instruments generally apply force to the interface between the bracket and the tooth that contains an appropriate orthodontic adhesive. In the situation of typical metal orthodontic brackets, the force that is applied deforms the orthodontic bracket which is substantially more ductile than the tooth or adhesive. Deformation of the bracket creates microcracks on and within the adhesive layer which ultimately results in bond failure. While such techniques have been generally accepted in removing metal orthodontic brackets, the debonding of ceramic brackets (for example, brackets made of alumina) is not easy to accomplish. This is due in part to the high rigidity of the ceramic materials used to form the bracket, thus deformation of the ceramic bracket does not occur. Therefore, the force needed to debond a ceramic bracket is substantially greater since tensile or shear mode of failure must occur as opposed to the peeling type of removal that occurs in metal type brackets. Additionally, ceramic brackets frequently use a chemical bonding system which provides extremely high bond strengths. The typical forces used to debond ceramic brackets can lead to substantial trauma to the patient, as well as the possibility of removing enamel from the tooth which is highly undesirable.
Several methods have been suggested in the prior art in order to minimize enamel damage and patient trauma during debonding of such brackets. One such method includes the application of heat to soften the adhesive. An example of this is illustrated in U.S. Pat. No. 4,907,965. Another method is a thorough cleaning of the bracket base periphery by dental burrs prior to debonding. Yet a third method requires use of a lever arm for applying a tortional load to the bracket. However, none of these proposed methods have been successful in either reducing patient trauma and/or reducing the possibility of enamel damage.
There has also been suggested in the prior art the removing of orthodontic brackets through ultrasonic devices of the magneto-restrictive type. However, such devices are not very efficient as they require the application of the ultrasonic tool for time periods upwards of 30 to 40 seconds per bracket. This is a substantial amount of time for the orthodontist to remove a bracket which generally results in substantial patient trauma and discomfort.
The present invention provides an improved orthodontic tool and method for fracturing the bond between two dental structures that is quick and does not cause any significant trauma to the patient.